In recent years it has been proposed to use various feed additives to achieve a fast growth in livestock, and in this respect antibiotic additives have attracted the greatest attention. Growth promoting antibiotic is the most common one among feed additives, mainly due to their positive effects in growth or feed conversion efficiency and also reduction of incidence of certain diseases. However, extensive use of antibiotic may cause animals to develop resistance in a number of pathogenic bacteria species (Mikkelsen and Jensen, 2000). Relatively good results have been attained with these additives. More recent findings have shown that such additives give rise to resistant bacteria strains in the livestock and it has also been established that the antibiotic substances are transferred in small amounts to humans. It has also been found that a certain risk exists for hyper sensitiveness in persons who handle such feed. In modern animal farming, various methods have been explored to improve animal health and growth performance. These include better husbandry management, nutrition and utilisation of feed additive. The common feed additives used are antibiotic, probiotics, enzymes and organic acids (Bernardeau et al., 2002). Likewise, cross-resistance may occur to therapeutic antibiotic belongs to the same class of drug, particularly those with close relationships with human antimicrobial therapies. In recent years, it has been proposed to use various feed additives to achieve a fast growth in livestock, and in this respect, antibiotic additives have attracted the greatest attention. It has now been found that by using a feed additive according to the present invention could be an advantage to eliminate the above mentioned disadvantages and still obtain result in livestock production which is at least as good as that previously attained by using antibiotic feed additives. Thus the desired result is obtained without the previous drawbacks.
Some countries already imposed restrictions or prohibitions on the use of antibiotics as growth promoters and this have drawn attention to possible alternatives (Wierup, 2000). During the last few years, research has focused on some valuable strains of lactic acid bacteria (LAB) and their potential use as probiotic agents. Probiotics are considered viable microbial preparations that promote mammalian health by preserving the natural microflora in the intestine. Probiotics are thought to attach to the intestinal mucosa, colonize the intestinal tract and thereby prevent attachment of harmful micro-organisms thereon. A prerequisite for their action resides in that they have to reach the gut's mucosa in a proper and viable form and especially do not get destroyed by the influence of the low pH prevailing in the stomach. In particular, the physiology of the digestive tract of cats and dogs differs from humans. For example, the average pH in the stomach is about 3.4 for dogs and 4.2 for cats. LAB as probiotic are often suggested as alternative for replacing antibiotic. LAB are widely used as starter cultures in meat and meat-products, play a very important role in ensuring the safety of different foods through the production of metabolites such as bacteriocins. Bacteriocins are proteinaceous compounds, which have antimicrobial properties that able to inhibit many different bacterial species, especially pathogenic bacteria (De Vuyst and Vandamme, 1994). These compounds have received a great attention because they are produced by beneficial to human health bacteria and also often used as natural food preservatives. It has been shown that administration of bacteriocins influences the bacterial ecology of the gastrointestinal tract and reduces the levels of pathogenic bacteria in different parts of gastrointestinal tract (van Winsen et al., 2001). Gaenzale et al. (1999) showed that bacteriocin curvacin produced by Lactobacillus curvatus inhibited Escherichia coli and Listeria inoculate in the stomach. It also has been shown that bacteriocins produced by Lactococcus lactis subspecies lactis have antibacterial properties (Mishra and Lambert, 1996). U.S. Pat. No. 5,968,569 discloses the inclusion of a probiotic microorganism in a pet food cereal, neither it, nor the remaining available art provides information concerning strains specifically intended for pet health. Thus, there is a need to provide novel bacterial strains that are particularly adapted for pets and that have been selected for their high probiotic properties beneficial for pet health and to incorporate these strains into a pet food composition.
It has been previously known that with the aid of LAB, one can utilize skim milk, buttermilk, and whey as animal feed. The products thus contain, in addition to lactic acid, vitamines, sugar and other carbohydrates but no viable microorganisms. The present invention concerns a growth promoting feed additive containing naturally occurring source of metabolites produced by Lactobacillus sp. The invention also relates to the use of an effective amount of metabolites obtained from Lactobacillus sp., and providing an optimum dosage of the most effective of metabolites as feed additives for improving the growth performance and overall health of poultry. This animal feed additive shall combine with nutrients to form an animal feed. Scientifically controlled experiments with animals have shown that the economic gain from animals raised on food furnished with additives according to the present invention is increased because the quality and value of the animal products are increased.